Abstract

Three genera and seven species belonging to thesubfamily Zigzagiceratinae (family Perisphinctidae) aredescribed from the Lower Bathonian of France and SaudiArabia. Intraspecific dimorphism is recognized. A revision ofthe genus Franchia proposed by Sturani (1967), based on thesyntypes and new specimens from south-east France, ispresented. Franchia arkelli Sturani, Franchia subalpina sp.nov., Protozigzagiceras torrensi (Sturani), Protozigzagicerastethycum sp. nov., Protozigzagiceras flexum sp. nov. and Protozigzagicerasdensum sp. nov. are described from the Digne–Castellane region of south-east France. Megazigzagicerassubarabicum, gen. et sp. nov. is described from the Dharmaregion of Saudi Arabia. The successive Early Bathonian speciesof Franchia and Protozigzagiceras herein identified inWest Tethyan areas, as members of the Mediterranean–CaucasianSubrealm, formed lasting separate peramorphoclinescharacterized by increasing hydrodynamic coiling of theshell. In contrast, rapid proterogenesis originated and diversifiedthe earliest Bathonian zigzagiceratin lineages, givingpaedomorphic members, commonly neotenic and more scarcelyprogenetic. Procerites–Siemiradzkia seems to be the oldestzigzagiceratin member in the French Subalpine, Iberianand Lusitanian basins, branched off by paedomorphosis fromleptosphinctins at the Bajocian–Bathonian transition. TheMediterranean–Caucasian genera Franchia, Zigzagiceras, Zigzagitesand Wagnericeras branched from successive species ofProtozigzagiceras, in turn, a direct derivative of Procerites.The oldest lineages of the clade Zigzagiceratinae evolved byiterative, rapid, paedomorphic changes and additional, lasting,peramorphic modifications during the Early Bathonian.